On the motion of dayside auroras caused by a solar wind pressure pulse
Global ultraviolet auroral images from the IMAGE satellite were used to investigate the dynamics of the dayside auroral oval responding to a sudden impulse (SI) in the solar wind pressure. At the same time, the TV all-sky camera and the EISCAT radar on Svalbard (in the pre-noon sector) allowed fo...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2005-02-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/23/509/2005/angeo-23-509-2005.pdf |
| _version_ | 1819237132315656192 |
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| author | A. Kozlovsky A. Kozlovsky V. Safargaleev N. Østgaard T. Turunen A. Koustov J. Jussila A. Roldugin |
| author_facet | A. Kozlovsky A. Kozlovsky V. Safargaleev N. Østgaard T. Turunen A. Koustov J. Jussila A. Roldugin |
| author_sort | A. Kozlovsky |
| collection | DOAJ |
| description | Global ultraviolet auroral images from the IMAGE satellite were used to
investigate the dynamics of the dayside auroral oval responding to a sudden
impulse (SI) in the solar wind pressure. At the same time, the TV all-sky
camera and the EISCAT radar on Svalbard (in the pre-noon sector) allowed for
detailed investigation of the auroral forms and the ionospheric plasma flow.
After the SI, new discrete auroral forms appeared in the poleward part of the
auroral oval so that the middle of the dayside oval moved poleward from about
70° to about 73° of the AACGM latitude. This poleward shift
first occurred in the 15 MLT sector, then similar shifts were observed in the
MLT sectors located more westerly, and eventually the shift was seen in the 6
MLT sector. Thus, the auroral disturbance "propagated" westward (from 15 MLT
to 6 MLT) at an apparent speed of the order of 7km/s. This motion of the
middle of the auroral oval was caused by the redistribution of the luminosity
within the oval and was not associated with the corresponding motion of the
poleward boundary of the oval. The SI was followed by an increase in the
northward plasma convection velocity. Individual auroral forms showed
poleward progressions with velocities close to the velocity of the northward
plasma convection. The observations indicate firstly a pressure
disturbance propagation through the magnetosphere at a velocity of the order
of 200km/s which is essentially slower than the velocity of the fast
Alfvén (magnetosonic) wave, and secondly a potential (curl-free)
electric field generation behind the front of the propagating disturbance,
causing the motion of the auroras. We suggest a physical explanation for the
slow propagation of the disturbance through the magnetosphere and a model for
the electric field generation. Predictions of the model are supported by the
global convection maps produced by the SuperDARN HF radars. Finally, the
interchange instability and the eigenmode toroidal Alfvén oscillations are
discussed as possible generation mechanisms for the dayside auroral forms
launched by the SI. |
| first_indexed | 2024-12-23T13:15:28Z |
| format | Article |
| id | doaj.art-0331b422863a424491d79962dff29c74 |
| institution | Directory Open Access Journal |
| issn | 0992-7689 1432-0576 |
| language | English |
| last_indexed | 2024-12-23T13:15:28Z |
| publishDate | 2005-02-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Annales Geophysicae |
| spelling | doaj.art-0331b422863a424491d79962dff29c742022-12-21T17:45:37ZengCopernicus PublicationsAnnales Geophysicae0992-76891432-05762005-02-012350952110.5194/angeo-23-509-2005On the motion of dayside auroras caused by a solar wind pressure pulseA. Kozlovsky0A. Kozlovsky1V. Safargaleev2N. Østgaard3T. Turunen4A. Koustov5J. Jussila6A. Roldugin7Sodankylä Geophysical Observatory, Sodankylä, FIN-99600, FinlandDepartment of Physical Sciences, University of Oulu, Oulu, FIN-90014, FinlandPolar Geophysical Institute, Apatity, 18 4200, RussiaSpace Sciences Laboratory, University of California, 7 Gauss Way, Berkeley, CA 94 720–7450, USASodankylä Geophysical Observatory, Sodankylä, FIN-99600, FinlandDepartment of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, SK S7N 5E2, CanadaDepartment of Physical Sciences, University of Oulu, Oulu, FIN-90014, FinlandPolar Geophysical Institute, Apatity, 18 4200, RussiaGlobal ultraviolet auroral images from the IMAGE satellite were used to investigate the dynamics of the dayside auroral oval responding to a sudden impulse (SI) in the solar wind pressure. At the same time, the TV all-sky camera and the EISCAT radar on Svalbard (in the pre-noon sector) allowed for detailed investigation of the auroral forms and the ionospheric plasma flow. After the SI, new discrete auroral forms appeared in the poleward part of the auroral oval so that the middle of the dayside oval moved poleward from about 70° to about 73° of the AACGM latitude. This poleward shift first occurred in the 15 MLT sector, then similar shifts were observed in the MLT sectors located more westerly, and eventually the shift was seen in the 6 MLT sector. Thus, the auroral disturbance "propagated" westward (from 15 MLT to 6 MLT) at an apparent speed of the order of 7km/s. This motion of the middle of the auroral oval was caused by the redistribution of the luminosity within the oval and was not associated with the corresponding motion of the poleward boundary of the oval. The SI was followed by an increase in the northward plasma convection velocity. Individual auroral forms showed poleward progressions with velocities close to the velocity of the northward plasma convection. The observations indicate firstly a pressure disturbance propagation through the magnetosphere at a velocity of the order of 200km/s which is essentially slower than the velocity of the fast Alfvén (magnetosonic) wave, and secondly a potential (curl-free) electric field generation behind the front of the propagating disturbance, causing the motion of the auroras. We suggest a physical explanation for the slow propagation of the disturbance through the magnetosphere and a model for the electric field generation. Predictions of the model are supported by the global convection maps produced by the SuperDARN HF radars. Finally, the interchange instability and the eigenmode toroidal Alfvén oscillations are discussed as possible generation mechanisms for the dayside auroral forms launched by the SI.https://www.ann-geophys.net/23/509/2005/angeo-23-509-2005.pdf |
| spellingShingle | A. Kozlovsky A. Kozlovsky V. Safargaleev N. Østgaard T. Turunen A. Koustov J. Jussila A. Roldugin On the motion of dayside auroras caused by a solar wind pressure pulse Annales Geophysicae |
| title | On the motion of dayside auroras caused by a solar wind pressure pulse |
| title_full | On the motion of dayside auroras caused by a solar wind pressure pulse |
| title_fullStr | On the motion of dayside auroras caused by a solar wind pressure pulse |
| title_full_unstemmed | On the motion of dayside auroras caused by a solar wind pressure pulse |
| title_short | On the motion of dayside auroras caused by a solar wind pressure pulse |
| title_sort | on the motion of dayside auroras caused by a solar wind pressure pulse |
| url | https://www.ann-geophys.net/23/509/2005/angeo-23-509-2005.pdf |
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